Flow path switching valve and manufacturing method therefor

ABSTRACT

The flow path switching valve includes (a) a valve body having an open flow path which opens on a predetermined surface over a predetermined length in a predetermined direction, (b) a main body having a plurality of ports which open on a facing surface facing the predetermined surface at an interval shorter than the predetermined length in the predetermined direction, and a plurality of connection flow paths connected to the plurality of ports, (c) plate springs attached on both ends of the valve body in the predetermined direction so as to support the valve body such that a predetermined gap is formed between the predetermined surface and the facing surface, the plate springs applying elastic force onto the valve body according to a movement amount of the valve body in the predetermined direction, and (d) an actuator which drives the valve body back and forth in the predetermined direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of International Patent ApplicationNo. PCT/JP2017/013413, filed on Mar. 30, 2017, which claims priority toJapan Patent Application No. 2016-068379 filed on Mar. 30, 2016 andJapan Patent Application No. 2016-145726 filed on Jul. 25, 2016, and theentire contents of these applications are incorporated by reference inthis specification.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a flow path switching valve forswitching a flow path for a fluid.

2. Description of the Related Art

A conventional flow path switching valve of such a type includes a spoolhaving a flow passage for fluid formed on its outer circumferentialsurface, and a sleeve which has a plurality of ports for allowing inflowand outflow of the fluid and which slidably houses the spool (seeJapanese Patent Application Laid-Open No. 2007-211857). In the valvedescribed in Japanese Patent Application Laid-Open No. 2007-211857, theflow path for the fluid is switched by reciprocating the spool in theaxial direction.

BRIEF DESCRIPTION OF THE INVENTION

Incidentally, in the valve described in Japanese Patent ApplicationLaid-Open No. 2007-211857, the spool and the sleeve rub against eachother upon switching of the fluid flow path. Therefore, when the spoolis driven, frictional force is produced, thereby lowering responsivenessin switching of the fluid flow path.

The present invention has been accomplished in view of suchcircumstances, and its main object is to provide a flow path switchingvalve which can improve the responsiveness in switching the fluid flowpath.

In order to solve the above-described problem, the present inventionemploys the following means.

The first aspect of the present invention is a flow path switching valvefor switching a flow path for a fluid. The flow path switching valvecomprises: a valve body which has an open flow passage which is open toa predetermined surface of the valve body over a predetermined length ina predetermined direction; a main body which has a plurality of portsformed at intervals in the predetermined direction shorter than thepredetermined length and being open to a facing surface of the main bodyfacing the predetermined surface and has connection flow passagesconnected to the plurality of ports, respectively; plate springs whichare attached to opposite end portions of the valve body in thepredetermined direction, respectively, which support the valve body suchthat a predetermined gap is formed between the predetermined surface andthe facing surface, and which apply elastic force to the valve body inaccordance with an amount of movement of the valve body in thepredetermined direction; and an actuator for reciprocating the valvebody in the predetermined direction.

According to the above-described configuration, through the connectionflow passages formed in the main body, the fluid can be caused to flowinto and flow out of the respective ports connected to the respectiveconnection flow passages. The valve body has an open flow passage whichis open to a predetermined surface of the valve body over apredetermined length in a predetermined direction. The main body has aplurality of ports formed at intervals in the predetermined directionshorter than the predetermined length and being open to a facing surfaceof the main body facing the predetermined surface. Therefore, the stateof connection of the plurality of ports through the open flow passage;i.e., the flow path for the fluid, can be switched by reciprocating thevalve body in the predetermined direction by the actuator.

Plate springs are attached to opposite end portions of the valve body inthe predetermined direction, respectively, and the plate springs supportthe valve body such that a predetermined gap is formed between thepredetermined surface and the facing surface. Therefore, the valve bodycan be reciprocated in a state in which the valve body and the main bodydo not rub against each other. Accordingly, it is possible to preventgeneration of frictional force during drive of the valve body andimprove the responsiveness in switching the flow path for the fluid.Further, since the plate springs apply elastic force to the valve bodyin accordance with the amount of movement of the valve body in thepredetermined direction, the elastic force of the plate springs can beutilized for control of the amount of movement of the valve body.

In accordance with one embodiment of the present invention, the openflow passage of the valve body may be open, over the predeterminedlength in the predetermined direction, to the predetermined surface andto an opposite surface of the valve body located opposite thepredetermined surface; the main body includes a first main body whichhas a plurality of ports formed at intervals in the predetermineddirection shorter than the predetermined length and being open to afirst facing surface of the first main body facing the predeterminedsurface and has connection flow passages connected to the plurality ofports, respectively, and a second main body which has a plurality ofports formed at intervals in the predetermined direction shorter thanthe predetermined length and being open to a second facing surface ofthe second main body facing the opposite surface and has connection flowpassages connected to the plurality of ports, respectively; and theplate springs support the valve body such that a first predetermined gapis formed between the predetermined surface and the first facing surfaceand a second predetermined gap is formed between the opposite surfaceand the second facing surface.

In the configuration in which the opposite end portions of the valvebody are supported by the plate springs, the valve body may move in adirection away from the ports due to the pressure of the fluid flowingfrom the ports toward the valve body.

In this regard, according to the above-described configuration, thefirst main body and the second main body are provided on opposite sidesof the valve body. A plurality of ports are formed in the first mainbody, and a plurality of ports which are the same as the ports of thefirst main body are formed in the second main body. Therefore, when thesame fluid is caused to flow through a port of the first main body andflow through a port of the second main body, which corresponds to theport of the first main body, the pressure produced by the fluid flowingfrom the port of the first main body toward the valve body and thepressure produced by the fluid flowing from the port of the second mainbody toward the valve body can be canceled out. Accordingly, it ispossible to prevent the valve body from moving in a direction away fromthe ports due to the pressure of the fluid flowing from the ports towardthe valve body.

Further, the plate springs support the valve body such that a firstpredetermined gap is formed between the predetermined surface and thefirst facing surface and a second predetermined gap is formed betweenthe opposite surface and the second facing surface. Therefore, the valvebody can be reciprocated in a state in which the valve body does not rubagainst the first main body and the second main body.

Specifically, according to one embodiment of the present invention,there can be employed a configuration in which each plate spring isattached to the main body such that main faces of the plate spring whichhave a largest area extend perpendicularly to the predetermineddirection. By virtue of such a configuration, it is possible to easilyrealize a structure in which the plate springs support the valve bodysuch that the predetermined gap between the predetermined surface of thevalve body and the facing surface of the main body is maintained, andthe plate springs apply to the valve body only elastic force in thepredetermined direction.

In accordance with one embodiment of the present invention, a movableelement may be fixed to a portion of the valve body, which portion islocated between the plate springs; and the actuator reciprocates thevalve body in the predetermined direction in a non-contact state by anelectromagnetic force applied to the movable element in a region betweenthe plate springs in the predetermined direction.

According to the above-described configuration, the valve body is drivenby the actuator in the predetermined direction in a non-contact state bymeans of the electromagnetic force applied to the movable element fixedto the valve body. As a result, no frictional force is generated duringdrive of the valve body, whereby the responsiveness in driving the valvebody can be improved. Also, since the movable element to whichelectromagnetic force is applied and the valve body can be formed asseparate members, the degree of freedom in designing the valve body canbe increased.

Furthermore, since the opposite end portions of the valve body aresupported by the plate springs, the electromagnetic force is applied tothe movable element in a region located between the plate springs in thepredetermined direction. Therefore, it is possible to prevent swaying ofthe valve body when the valve body is driven.

In accordance with one embodiment of the present invention, in theactuator, a position of the valve body in a state in which the platesprings support the valve body in their natural state is set to aneutral position at which the electromagnetic force for reciprocatingthe valve body in the predetermined direction is not applied.

According to the above-described configuration, in a state in which theplate springs support the valve body in the natural state and noelectromagnetic force is applied by the actuator, the valve body can bemaintained at the neutral position in the predetermined direction.Therefore, by controlling the electromagnetic force applied to themovable element while using the neutral position as a reference, thevalve body can be easily reciprocated in the predetermined direction.

In accordance with one embodiment of the present invention, the actuatormay include a movable rod which extends through the plate springs andthe valve body and is attached to the valve body, and the actuatorreciprocates the movable rod in the predetermined direction.

According to the above-described configuration, the movable rod of theactuator extends through the plate springs and the valve body and isattached to the valve body. Therefore, the predetermined surface of thevalve body and the facing surface of the main body can be easilymaintained parallel to each other.

In accordance with one embodiment of the present invention, the actuatormay reciprocate the movable rod in a non-contact state byelectromagnetic force.

According to the above-described configuration, the movable rod of theactuator is reciprocated in a non-contact state by electromagneticforce. Accordingly, generation of frictional force during drive of thevalve body can be prevented in the actuator too, whereby theresponsiveness in switching the flow path for the fluid can be improvedfurther.

In accordance with one embodiment of the present invention, in theactuator, a position of the movable rod in a state in which the platesprings support the valve body in their natural state may be set to aneutral position at which the electromagnetic force for reciprocatingthe movable rod in the predetermined direction is not applied.

According to the above-described configuration, in a state in which theplate springs support the valve body in the natural state and noelectromagnetic force is applied by the actuator, the movable rod can bemaintained at the neutral position in the predetermined direction.Therefore, by controlling the electromagnetic force applied to themovable element while using the neutral position as a reference, themovable rod and thus the valve body can be easily reciprocated.

In accordance with one embodiment of the present invention, each of thepredetermined surface and the facing surface may be finished to have apredetermined degree of flatness; and the plate springs support thevalve body such that the predetermined surface and the facing surfacehave a predetermined degree of parallelism therebetween.

According to the above-described configuration, the degrees of flatnessand parallelism of the predetermined surface of the valve body and thefacing surface of the main body are controlled. Therefore, the accuracyof the predetermined gap formed between the predetermined surface andthe facing surface can be improved.

Another aspect of the present invention provides a method formanufacturing the flow path switching valve of one or more of theabove-described embodiments, characterized in that, after the platesprings are fixed to the main body in a state in which a gap jig havinga thickness set on the basis of a size of the predetermined gap isinserted between the predetermined surface and the facing surface, thegap jig is removed.

According to the above-described process, a gap jig having a thicknessset on the basis of the width of the predetermined gap is insertedbetween the predetermined surface of the valve body and the facingsurface of the main body. Therefore, the spacing between thepredetermined surface and the facing surface can be easily adjusted tothe predetermined gap. Since the gap jig is removed after the platesprings are fixed to the main body in such a state, the predeterminedgap can be easily formed between the predetermined surface and thefacing surface.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, and advantages of the presentdisclosure will be apparent from the following description when taken inconjunction with the accompanying drawings.

FIG. 1 is a perspective sectional view showing a flow path switchingvalve.

FIG. 2 is a perspective view showing a valve body, a main body, andplate springs of a first embodiment.

FIG. 3 is a sectional view showing the valve body, the main body, andthe plate springs of the first embodiment.

FIG. 4 is a schematic view showing the valve body and the main body ofthe first embodiment.

FIG. 5 is a perspective view showing an actuator.

FIG. 6 is a perspective sectional view showing the actuator in anunexcited state.

FIG. 7 is a perspective sectional view showing the actuator in apositive direction excited state.

FIG. 8 is a perspective sectional view showing the actuator in anegative direction excited state.

FIG. 9 is a schematic view showing deformation of the plate springs ofthe first embodiment.

FIG. 10 is a graph showing a relation between current supplied to a coiland stroke of the valve body in the first embodiment.

FIG. 11 is a graph showing a relation between current supplied to thecoil and flow rate of air in the first embodiment.

FIG. 12 is a perspective view showing a valve body, main bodies, andplate springs of a second embodiment.

FIG. 13 is a sectional view showing the valve body, the main bodies, andthe plate springs of the second embodiment.

FIG. 14 is a schematic view showing the valve body and the main bodiesof the second embodiment.

FIG. 15 is a graph showing a relation between current supplied to a coiland flow rate of air in the second embodiment.

FIG. 16 is a time chart showing input and output values of flow rate ofthe second embodiment.

FIG. 17 is another time chart showing the input and output values offlow rate of the second embodiment.

FIG. 18 is another time chart showing the input and output values offlow rate of the second embodiment.

FIG. 19 is another time chart showing the input and output values offlow rate of the second embodiment.

FIG. 20 is a perspective sectional view showing a flow path switchingvalve of a third embodiment.

FIG. 21 is a perspective sectional view showing the flow path switchingvalve of the third embodiment.

FIG. 22 is a perspective sectional view showing a valve mechanism of thethird embodiment.

FIG. 23 is a front sectional view showing a state in which the valvemechanism is unexcited in the third embodiment.

FIG. 24 is a front sectional view showing a state in which the valvemechanism is excited in a positive direction in the third embodiment.

FIG. 25 is a front sectional view showing a state in which the valvemechanism is excited in a negative direction in the third embodiment.

FIG. 26 is a perspective sectional view showing a modification of thevalve mechanism of the third embodiment.

FIG. 27 is a graph showing an example of the relation between drivecurrent and flow rate in the third embodiment.

FIG. 28 is a graph showing a modified example of the relation betweendrive current and flow rate in the third embodiment.

FIG. 29 is a graph showing another modified example of the relationbetween drive current and flow rate in the third embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION First Embodiment

A first embodiment of a flow path switching valve for switching betweena flow passage for supplying air to a load (volume) and a flow passagefor discharging air from the load will now be described with referenceto the drawings.

As shown in FIG. 1, the flow path switching valve 10 includes a valvemechanism 20 and an actuator 70. The valve mechanism 20 and the actuator70 are connected to each other through a connection member 24. Theactuator 70 drives the valve mechanism 20.

The valve mechanism 20 includes a housing 21, a valve body 31, a mainbody 41, plate springs 51, a cover 27, etc.

The housing 21 has a rectangular tubular shape. The housing 21 has a P0port (pressurized air port) to which pressurized air (corresponding tofluid) is supplied, an A0 port (output port) from which air is suppliedto the load and to which air is discharged from the load, and an R0 port(discharge port) from which air is discharged. The housing 21 has apressurization flow passage, an output flow passage, and an airdischarge flow passage which are connected to the P0 port, the A0 port,and the R0 port, respectively, and are open to the inner surface of thehousing 21.

The valve body 31, the main body 41, the plate springs 51, etc. aredisposed inside the housing 21. As shown in FIGS. 2 to 4, the main body41 has a grooved shape (the shape of a rectangular tube having an openside). The main body 41 is fixed to the housing 21. The valve body 31has the shape of a rectangular parallelepiped. The valve body 31 isdisposed between inner side surfaces 41 b of the main body 41 which faceeach other. A gap is formed between the outer side surface of the valvebody 31 and each of the inner side surfaces 41 b of the main body 41.Namely, the outer side surface of the valve body 31 does not contactwith the inner side surfaces 41 b of the main body 41.

As shown in FIG. 4, the valve body 31 has an open flow passage 32 whichis formed on a predetermined surface 31 a (specifically, the lowersurface) of the valve body 31 and which is open over a predeterminedlength L1 in the longitudinal direction of the valve body 31(corresponding to the predetermined direction). The open flow passage 32is a recess in the shape of an oval hole whose length along the majoraxis is the predetermined length L1. As shown in FIGS. 2 and 3, thevalve body 31 has a through hole 33 which extends therethrough in thelongitudinal direction. The valve body 31 has pin holes 34 and screwholes 35 which extend therethrough in the vertical direction. Pin holesand screw holes are formed in a lower bottom portion of the main body 41at positions corresponding to the pin holes 34 and the screw holes 35,respectively.

The lower bottom portion of the main body 41 has a P1b port, an A1bport, and an R1b port (corresponding to the plurality of ports) whichare open to the facing surface 41 a which faces the predeterminedsurface 31 a of the valve body 31. The P1b port, the A1b port, and theR1b port are formed at intervals in the longitudinal direction of thevalve body 31, which intervals are shorter than the predetermined lengthL1. The lower bottom portion of the main body 41 has connection flowpassages 42, 43, and 44 which are connected to the P1b port, the A1bport, and the R1b port, respectively. The connection flow passages 42,43, and 44 are open on the lower surface of the lower bottom portion ofthe main body 41. The openings of the connection flow passages 42, 43,and 44 on the lower surface of the lower bottom portion of the main body41 serve as a P1a port, an A1a port, and an R1a port, respectively. TheP1a port, the A1a port, and the R1a port are connected to theabove-described pressurization flow passage, output flow passage, andair discharge flow passage, respectively.

As shown in FIGS. 1 and 2, the plate springs 51 are respectivelyattached to opposite end portions 36 of the valve body 31, which arelocated on the opposite sides in the longitudinal direction thereof.Each of the plate springs 51 is formed of a spring material such asspring steel and has the shape of a rectangular plate. Each plate spring51 has slits 51 a formed at predetermined positions. As a result offormation of the slits 51 a in the plate springs 51, the plate springs51 each have a predetermined meandering pattern. The thickness of theplate springs 51 is determined such that each of the plate springs 51has a predetermined rigidity and generates a predetermined elasticforce. Two short-side portions 51 b of each plate spring 51 are fixed tothe main body 41. Each plate spring 51 is fixed to the main body 41 suchthat its main faces (vertical surfaces in FIG. 2) having the largestarea extend perpendicularly to the longitudinal direction of the valvebody 31.

The predetermined surface 31 a of the valve body 31 and the facingsurface 41 a of the main body 41 are finished to have a predetermineddegree of flatness. The plate springs 51 support the valve body 31 suchthat the predetermined surface 31 a and the facing surface 41 a have apredetermined degree of parallelism therebetween. Specifically, theopposite longitudinal end portions 36 of the valve body 31 penetrate thecenters of the plate springs 51 and are fixed thereto. As shown in FIG.4, the plate springs 51 support the valve body 31 such that apredetermined gap C1 is formed between the predetermined surface 31 a ofthe valve body 31 and the facing surface 41 a of the main body 41. Thesize of the predetermined gap C1 is about 5 μm. A gap is formed betweenthe main body 41 and a surface of the valve body 31 on the side oppositethe predetermined surface 31 a. Namely, the valve body 31 has no portionwhich is in sliding engagement with other members.

The plate springs 51 apply elastic force to the valve body 31 inaccordance with the amount of movement of the valve body 31 in thelongitudinal direction of the valve body 31 (a direction orthogonal tothe main faces of the plate springs 51). Specifically, the plate springs51 apply to the valve body 31 an elastic force which is proportional tothe amount of movement of the valve body 31 in the longitudinaldirection of the valve body 31.

Next, a method for manufacturing the valve mechanism 20 (the flow pathswitching valve 10) will be described.

First, a gap jig is disposed on the upper surface (the facing surface 41a) of the lower bottom portion of the main body 41. The thickness of thegap jig is set on the basis of the size of the predetermined gap C1.Namely, the thickness of the gap jig is determined such that thepredetermined gap C1 is formed between the predetermined surface 31 a ofthe valve body 31 and the facing surface 41 a of the main body 41 afterassembly of the valve mechanism 20.

Subsequently, the valve body 31 is disposed on the gap jig in such amanner that the gap jig is sandwiched between the facing surface 41 a ofthe main body 41 and the lower surface (the predetermined surface 31 a)of the valve body 31. At that time, a gap is formed between the innersurface 41 b of the main body 41 and the outer surface of the valve body31.

Subsequently, the opposite longitudinal end portions 36 of the valvebody 31 are inserted into the through holes of the plate springs 51formed at their centers. Central portions of the plate springs 51 arethen fixed to the end portions 36 of the valve body 31 by means ofwelding. Also, the short-side portions 51 b of the plate springs 51 arefixed to the main body 41 by means of welding.

Subsequently, the gap jig is removed from the main body 41 and the valvebody 31. Thus, the assembly of the main body 41, the valve body 31, andthe plate springs 51 is completed.

Next, the structure of the actuator 70 will be described with referenceto FIGS. 1 and 5. The actuator 70 includes cores 71, coils 72, a cover73, magnets 74 and 75, a movable element 76, a movable rod 81, etc.

Each of the cores 71 is formed of a paramagnetic material and has theshape of a quadrangular prism. The coils 72 are wound around the outercircumferences of the cores 71. The paired cores 71 and coils 72 aredisposed parallel to each other (juxtaposed to each other). The paredcores 71 are connected to each other through the cover 73. The cover 73is formed of a paramagnetic material and has a plate-like shape.

One end portions of the cores 71 protrude from the coils 72. The one endportions of the cores 71 have respective parallel portions 71 a whichare flat surfaces parallel to each other.

The magnets 74 and 75 are attached to the pair of parallel portions 71a. The magnets 74 and 75 are permanent magnets formed of a ferromagneticmaterial. Each of the magnets 74 and 75 has the shape of a rectangularparallelepiped. The magnets 74 and 75 are attached to the parallelportions 71 a of the cores 71 such that their N and S poles are arrangedin the axial direction of the cores 71 (the longitudinal direction ofthe valve body 31). The N pole of the magnet 74 and the S pole of themagnet 75 face each other, and the S pole of the magnet 74 and the Npole of the magnet 75 face each other. Namely, the magnets 74 and 75 aredisposed such that the order of arrangement of the poles of the magnet74 in the axial direction of the cores 71 is reverse to that of thepoles of the magnet 75. The surfaces of the magnets 74 and 75 which faceeach other are parallel to each other.

The movable element 76 is disposed between the magnet 74 and the magnet75 via a portion of the above-described connection member 24. Theconnection member 24 is formed of a non-magnetic material. A portion ofthe connection member 24, which portion is disposed between the magnet74 and the magnet 75, is formed to be thin so that magnetic fluxeseasily pass through that portion. The movable element 76 is formed of aparamagnetic material and has the shape of a quadrangular prism. Themovable element 76 has a through hole 76 a which extends through themovable element 76 in the longitudinal direction of the valve body 31(the axial direction of the movable element 76).

The movable rod 81 of the actuator 70 extends through the through hole76 a of the movable element 76. The movable rod 81 is formed of anon-magnetic material and has a circular columnar shape. The movable rod81 has a small diameter portion, an intermediate diameter portion, and alarge diameter portion. The small diameter portion extends through thetwo plate springs 51 and the through hole 33 of the valve body 31, andthe intermediate diameter portion extends through the through hole 76 aof the movable element 76. One end portion 36 of the valve body 31 is incontact with a stepped portion between the small diameter portion andthe intermediate diameter portion.

In the longitudinal direction of the valve body 31, the movable element76 is located at the center positions of the magnets 74 and 75 (itsneutral position) due to the magnetic forces of the magnets 74 and 75.In order that the movable element 76 is fixed to the movable rod 81 inthis state, the relative position of the movable element 76 and themovable rod 81 is adjusted by a spacer 82. The movable element 76 or thespacer 82 is brought into engagement with a step between theintermediate diameter portion and the large diameter portion of themovable rod 81, and a nut 83 is attached to the intermediate diameterportion for fastening, whereby the movable element 76 is attached to themovable rod 81.

Also, in a state in which the two plate springs 51 are in their naturalstate, the small diameter portion of the movable rod 81 extends throughthe valve body 31 and the two plate springs 51. In this state, a nut 37is attached to a distal end of the small diameter portion for fastening,whereby the small diameter portion is attached to the valve body 31.Namely, in the actuator 70, the positions of the movable element 76 andthe movable rod 81 in a state in which the plate springs 51 support thevalve body 31 in the natural state are set to a neutral position atwhich the electromagnetic force for reciprocating the movable rod 81(the movable element 76) in the longitudinal direction of the valve body31 is not applied. A gap is formed between the nut 37 and the cover 27,and the nut 37 is not in contact with the cover 27.

An end potion of the large diameter portion of the movable rod 81 iscovered with an end member 84. The end member 84 is formed of anon-magnetic material. A space which is defined by the cover 27, thehousing 21, the connection member 24, and the end member 84 and in whichthe main body 41, the valve body 31, the movable rod 81, the movableelement 76, etc. are accommodated is kept airtight (sealed) by O-rings85, 86, and 87 (seal members). A gap is formed between “the movable rod81, the movable element 76, the spacer 82, and the nut 83” and “theconnection member 24 and the end member 84.” Namely, the movable rod 81,the movable element 76, the spacer 82, and the nut 83 are not in contactwith the connection member 24 and the end member 84.

Next, the principle of reciprocating the movable rod 81 and the valvebody 31 in the longitudinal direction of the valve body 31 by theactuator 70 will be described with reference to FIGS. 6 to 8.

In an unexcited state in which no current is supplied to the coils 72 ofthe actuator 70, as shown in FIG. 6, a magnetic field extending from theN pole of the magnet 74 toward the S pole of the magnet 75 and amagnetic field extending from the N pole of the magnet 75 toward the Spole of the magnet 74 are generated. In this state, the movable element76 is at rest in the neutral position in the axial direction of themovable rod 81 (the longitudinal direction of the valve body 31) becausethe generated magnetic fields are in balance. In this state, since theplate springs 51 are in the natural state, no force is applied from theplate springs 51 to the movable rod 81. Also, in this state, the P1bport and the R1b port of the main body 41 are closed by the valve body31 as shown in FIG. 4.

In a positive direction excited state in which a current of a positivedirection is supplied to the coils 72 of the actuator 70, a coilmagnetic field extending from the parallel portion 71 a of the uppercore 71 toward the parallel portion 71 a of the lower core 71 isgenerated as indicated by an arrow H1 in FIG. 7. Therefore, the magneticfield extending from the N pole of the magnet 74 toward the S pole ofthe magnet 75 and the coil magnetic field strengthen each other, and themagnetic field extending from the N pole of the magnet 75 toward the Spole of the magnet 74 and the coil magnetic field weaken each other. Asa result, the movable element 76 receives a magnetic attraction forcetoward the valve body 31. Thus, as indicated by an arrow F1, the movablerod 81 and the valve body 31 move, together with the movable element 76,in the direction of the arrow F1. At that time, by means ofelectromagnetic force, the actuator 70 drives the movable rod 81 in anon-contact state, whereby the valve body 31 is driven without cominginto contact with the main body 41. When the valve body 31 is driven, asindicated by arrows F3 in FIG. 9, the plate springs 51 apply to thevalve body 31 a reaction force which is proportional to the amount ofmovement of the valve body 31. In FIG. 4, when the valve body 31 ismoved leftward (toward the cover 27), the A1b port and the R1b port ofthe main body 41 are connected through the open flow passage 32 of thevalve body 31. Namely, the flow passage of the flow path switching valve10 is switched.

In a negative direction excited state in which a current of a negativedirection is supplied to the coils 72 of the actuator 70, a coilmagnetic field extending from the parallel portion 71 a of the lowercore 71 toward the parallel portion 71 a of the upper core 71 isgenerated as indicated by an arrow H2 in FIG. 8. Therefore, the magneticfield extending from the N pole of the magnet 74 toward the S pole ofthe magnet 75 and the coil magnetic field weaken each other, and themagnetic field extending from the N pole of the magnet 75 toward the Spole of the magnet 74 and the coil magnetic field strengthen each other.As a result, the movable element 76 receives a magnetic attraction forcetoward the end member 84 (the side opposite the valve body 31). Thus, asindicated by an arrow F2, the movable rod 81 and the valve body 31 move,together with the movable element 76, in the direction of the arrow F2.At that time, by means of electromagnetic force, the actuator 70 drivesthe movable rod 81 in a non-contact state, whereby the valve body 31 isdriven without coming into contact with the main body 41. When the valvebody 31 is driven, the plate springs 51 apply to the valve body 31 areaction force which is proportional to the amount of movement of thevalve body 31. In FIG. 4, when the valve body 31 is moved rightward(toward the end member 84), the A1b port and the P1b port of the mainbody 41 are connected through the open flow passage 32 of the valve body31. Namely, the flow passage of the flow path switching valve 10 isswitched.

The load generated by the plate springs 51 is in proportional to thestroke of the valve body 31. Also, the smaller the thickness of theplate springs 51, the longer the stroke for the same plate spring load.

FIG. 10 is a graph showing the relation between the current supplied tothe coils 72 and the stroke of the valve body 31. The stroke in thepositive direction increases as the current in the positive direction isincreased, and the stroke in the negative direction increases as thecurrent in the negative direction is increased.

FIG. 11 is a graph showing the relation between the current supplied tothe coils 72 and the flow rate of air. Continuous lines show the resultsof an experiment performed for the case where the pressure of air is 0.1MPa, and broken lines show the results of an experiment performed forthe case where the pressure of air is 0.2 MPa. In both the case wherethe pressure is 0.1 MPa and the case where the pressure is 0.2 MPa, theflow rate from the A port (the A0 port) to the R port (the R0 port)increases as the current in the positive direction is increased, and theflow rate from the P port (the P0 port) to the A port (the A0 port)increases as the current in the negative direction is increased. In thecase where the pressure is 0.2 MPa, the flow rate for the same currentis greater than that in the case where the pressure is 0.1 MPa.

The present embodiment having been described in detail above has thefollowing advantages.

The plate springs 51 are attached to the opposite end portions 36 of thevalve body 31 located on opposite sides in the longitudinal direction ofthe valve body 31 (the predetermined direction). The plate springs 51support the valve body 31 such that the predetermined gap C1 is formedbetween the predetermined surface 31 a of the valve body 31 and thefacing surface 41 a of the main body 41. Therefore, the valve body 31can be reciprocated in a state in which the valve body 31 and the mainbody 41 do not rub against each other. Accordingly, it is possible toprevent generation of frictional force during driving of the valve body31 and improve the responsiveness in switching the flow path for air.Further, since the plate springs 51 apply elastic force to the valvebody 31 in accordance with the amount of movement of the valve body 31in the above-described predetermined direction, the elastic force of theplate springs 51 can be utilized for control of the amount of movementof the valve body 31.

The plate springs 51 are fixed to the main body 41 such that the mainfaces of the plate springs 51 having the largest area extendperpendicularly to the predetermined direction. Therefore, the platesprings 51 can easily realize a structure in which the plate springs 51support the valve body 31, while maintaining the predetermined gap C1between the predetermined surface 31 a of the valve body 31 and thefacing surface 41 a of the main body 41, and apply to the valve body 31only elastic force along the predetermined direction.

The actuator 70 includes the movable rod 81 which extends through theplate springs 51 and the valve body 31 and is attached to the valve body31 and reciprocates the movable rod 81 in the predetermined direction.In this configuration, since the movable rod 81 of the actuator 70extends through the plate springs 51 and the valve body 31 and isattached to the valve body 31, the predetermined surface 31 a of thevalve body 31 and the facing surface 41 a of the main body 41 can beeasily maintained parallel to each other.

The movable rod 81 of the actuator 70 is reciprocated in a non-contactstate by means of electromagnetic force. Accordingly, even in theactuator 70, it is possible to prevent generation of frictional forceduring driving of the valve body 31, thereby further improving theresponsiveness in switching the flow path for air.

In the actuator 70, the position of the movable rod 81 (the movableelement 76) in a state in which the plate springs 51 support the valvebody 31 in the natural state is set to the neutral position at which theelectromagnetic force for reciprocating the movable rod 81 in thepredetermined direction is not applied. By virtue of this configuration,in a state in which the plate springs 51 support the valve body 31 inthe natural state and no electromagnetic force is applied by theactuator 70, the movable rod 81 can be maintained at the neutralposition in the predetermined direction. Therefore, by controlling theelectromagnetic force applied to the movable rod 81 while using theneutral position as a reference, the movable rod 81 and thus the valvebody 31 can be easily reciprocated.

The predetermined surface 31 a of the valve body 31 and the facingsurface 41 a of the main body 41 are finished to have a predetermineddegree of flatness. The plate springs 51 support the valve body 31 suchthat the predetermined surface 31 a and the facing surface 41 a have apredetermined degree of parallelism therebetween. According to such aconfiguration, the degrees of flatness and parallelism of thepredetermined surface 31 a of the valve body 31 and the facing surface41 a of the main body 41 are controlled. Therefore, it is possible toincrease the accuracy of the predetermined gap C1 formed between thepredetermined surface 31 a and the facing surface 41 a.

Since the predetermined gap C1 is formed between the predeterminedsurface 31 a of the valve body 31 and the facing surface 41 a of themain body 41, even in a state in which the P1b port is not connected tothe open flow passage 32 as shown in FIG. 4, air flowing from the P1bport toward the valve body 31 leaks through the predetermined gap C1.Since the size of the predetermined gap C1 is about 5 μm, the amount ofair leaking through the predetermined gap C1 can be decreased.

Since a gap jig having a thickness set on the basis of the size of thepredetermined gap C1 is inserted between the predetermined surface 31 aand the facing surface 41 a, the spacing between the predeterminedsurface 31 a and the facing surface 41 a can be easily adjusted to thepredetermined gap C1. Since the gap jig is removed after the platesprings 51 are fixed to the main body 41 in such a state, thepredetermined gap C1 can be easily formed between the predeterminedsurface 31 a and the facing surface 41 a.

As shown in FIG. 6, the magnets 74 and 75 have the shape of arectangular parallelepiped. Therefore, as shown in FIGS. 8 and 9, whenthe actuator 70 is brought into an excited state, only magnetic forcesin the directions indicated by arrows F1 and F2 act on the movableelement 76 and the movable rod 81, and magnetic forces in the directionorthogonal to the predetermined surface 31 a of the valve body 31 (thesheet on which FIGS. 8 and 9 are depicted) do not act on the movableelement 76 and the movable rod 81. Accordingly, it is possible toprevent the movable rod 81 from shifting in the direction orthogonal tothe predetermined surface 31 a. In contrast, in the case where each ofthe magnets 74 and 75 has the shape of a semicylinder, the magneticforces in the direction orthogonal to the predetermined surface 31 a acton the movable element 76 and the movable rod 81, and due to themagnetic force imbalance, the movable rod 81 may shift in the directionorthogonal to the predetermined surface 31 a.

In the above-described first embodiment, the amount of air leakingthrough the predetermined gap C1 is reduced by setting the size of thepredetermined gap C1 to about 5 μm. However, as shown in FIG. 11, evenwhen the magnitude of current is zero, a flow rate due to the leakage ofair exists. In particular, in the case where the pressure of air is 0.2MPa, the flow rate due to the leakage of air is greater than that in thecase where the pressure of air is 0.1 MPa.

Conceivably, the above-mentioned phenomenon occurs for the followingreason. In the structure in which the opposite end portions 36 of thevalve body 31 are supported by the plate springs 51, as shown in FIG. 4,the valve body 31 moves in a direction away from the P1b port and theA1b port due to the pressure of air flowing from the P1b port and theA1b port toward the valve body 31. Namely, the pressure of air may widenthe predetermined gap C1 between the predetermined surface 31 a of thevalve body 31 and the facing surface 41 a of the main body 41.

Second Embodiment

In order to overcome the above-mentioned drawback, in the presentembodiment, a first main body 41A and a second main body 41B areprovided on opposite sides of the valve body 31 as shown in FIGS. 12 to14. In the below, a portion of the second embodiment different from thatof the first embodiment will be mainly described. Notably, members whichcorrespond to those of the first embodiment are denoted by the samereference numerals, and their descriptions will not be repeated.

In the valve body 31, the open flow passage 32 is open to thepredetermined surface 31 a of the valve body 31 and to an oppositesurface 31 b on the side opposite the predetermined surface 31 a andextends over a predetermined length L1 in the longitudinal direction ofthe valve body 31 (corresponding to the predetermined direction). Theopen flow passage 32 extends through the valve body 31 from thepredetermined surface 31 a to the opposite surface 31 b. Notably, therecan be employed a structure in which open flow passages 32 areindividually formed on the predetermined surface 31 a side and theopposite surface 31 b side of the valve body 31 and none of the openflow passages 32 extends from the predetermined surface 31 a to theopposite surface 31 b.

In the first main body 41A, a P1b port, an A1b port, and an R1b portwhich are open to a first facing surface 45 a which faces thepredetermined surface 31 a are formed at intervals (shorter than thepredetermined length L1) in the longitudinal direction of the valve body31. In the second main body 41B, a P1b port, an A1b port, and an R1bport which are open to a second facing surface 45 b which faces theopposite surface 31 b are formed at intervals (shorter than thepredetermined length L1) in the longitudinal direction of the valve body31. The P1b port, A1b port, and R1b port of the first main body 41A facethe P1b port, A1b port, and R1b port, respectively, of the second mainbody 41B. The connection flow passages 42, 43, and 44 are connected tothe P1b ports, the A1b ports, and the R1b ports, respectively.

A third main body 41C is provided between the first main body 41A andthe second main body 41B. The short-side portions 51 b of the platesprings 51 are fixed, by means of welding, to opposite ends of the thirdmain body 41C located on opposite sides in the longitudinal direction.The first main body 41A and the second main body 41B are fixed to thethird main body 41C using screws 45. The plate springs 51 support thevalve body 31 such that a first predetermined gap C1 is formed betweenthe predetermined surface 31 a and the first facing surface 45 a and asecond predetermined gap C2 is formed between the opposite surface 31 band the second facing surface 45 b. In the present embodiment, the firstpredetermined gap C1 and the second predetermined gap C2 are set suchthat their sizes are equal to each other. Notably, the main bodies 41A,41B, and 41C, the valve body 31, and the plate springs 51 are assembledby an assembling method similar to the assembling method of the firstembodiment.

The same pressurized air is supplied to the P1b port of the first mainbody 41A and to the P1b port of the second main body 41B whichcorresponds to the P1b port of the first main body 41A. As a result, thepressure produced by air flowing from the P1b port of the first mainbody 41A toward the valve body 31 and the pressure produced by airflowing from the P1b port of the second main body 41B toward the valvebody 31 are canceled out.

FIG. 15 is a graph showing the relation between the current supplied tothe coils 72 and the flow rate of air. In FIG. 15, the flow rate due tothe leakage of air decreases as compared with FIG. 11. Since the amountof leakage of air decreases, the maximum value of the flow rate can beincreased even when air of a lower pressure is used.

FIGS. 16 to 19 are time charts showing the input value (input) andoutput value (output) of the flow rate.

FIG. 16 shows the case where the flow path switching valve 10 is used tosupply air to and discharge air from a 3 cc load (volume) and a stepwiseinput value (instruction value) is applied. Although slight overshootoccurs at moments when the input value changes, the output valuecoincides with the input value.

FIG. 17 shows the case where the flow path switching valve 10 is used tosupply air to and discharge air from a 3 cc load (volume) and asinusoidal input value having a frequency of 10 Hz is applied. Althoughslight overshoot occurs in the vicinity of the local maximum and minimumof the sine wave, the output value coincides with the input value.

FIG. 18 shows the case where the flow path switching valve 10 is used tosupply air to and discharge air from a 3 cc load (volume) and asinusoidal input value having a frequency of 2 Hz is applied. In thiscase, the output value accurately coincides with the input value.

FIG. 19 shows the case where the flow path switching valve 10 is used tosupply air to and discharge air from an 80 cc load (volume) and astepwise input value is applied. In this case, the output valueaccurately coincides with the input value.

The present embodiment having been described in detail above has thefollowing advantages. Here, only the advantages different from those ofthe first embodiment will be described.

The first main body 41A and the second main body 41B are provided onopposite sides with the valve body 31 intervening therebetween. The sameports; i.e., the P1b port, the A1b port, and the R1b port, are formed ineach of the first main body 41A and the second main body 41B. Therefore,when the same air is caused to flow through the P1b port, the A1b port,and the R1b port of the first main body 41A and flow through the P1bport, the A1b port, and the R1b port of the second main body 41B, whichcorrespond to the P1b port, the A1b port, and the R1b port of the firstmain body 41A, the pressure produced by air flowing from the P1b port orthe A1b port of the first main body 41A toward the valve body 31 and thepressure produced by air flowing from the P1b port or the A1b port ofthe second main body 41B toward the valve body 31 can be canceled out.Accordingly, it is possible to prevent the valve body 31 from moving ina direction away from the P1b port and the A1b port due to the pressureof air flowing from the P1b port or the A1b port toward the valve body31.

The pressure produced by air flowing from the ports of the first mainbody 41A toward the valve body 31 and the pressure produced by airflowing from the ports of the second main body 41B toward the valve body31 can be canceled out. Therefore, the required rigidity of the platesprings 51 can be decreased, and plate springs thinner than those usedin the first embodiment can be employed as the plate springs 51.

The plate springs 51 support the valve body 31 such that a firstpredetermined gap C1 is formed between the predetermined surface 31 a ofthe valve body 31 and the first facing surface 45 a and a secondpredetermined gap C2 is formed between the opposite surface 31 b of thevalve body 31 and the second facing surface 45 b. Therefore, the valvebody 31 can be reciprocated in a state in which the valve body 31 doesnot rub against the first and second main bodies 41A and 41B.

The above-described first and second embodiments may be modified asfollows.

The number and shape of the gap jig(s) used for assembling the main body41 (41A, 41B, 41C), the valve body 31, and the plate springs 51 can bechanged arbitrarily. Namely, the numbers and shapes can be changedarbitrarily so long as the thickness of the gap jig(s) is set on thebasis of the size of the predetermined gap C1 between the predeterminedsurface 31 a of the valve body 31 and the facing surface 41 a (45 a) ofthe main body 41.

The size of the predetermined gap C1 is not limited to about 5 μm, andmay be 1 to 5 μm, 6 to 10 μm, or 10 to 20 μm.

A structure in which the movable rod 81 penetrates halfway the valvebody 31 or a structure in which the movable rod 81 is fixed to an endportion 36 of the valve body 31 on one side thereof can be employed.

In the actuator 70, the position of the movable rod 81 (the movableelement 76) in a state in which the plate springs 51 support the valvebody 31 in the natural state may be set to a position other than theneutral position at which the electromagnetic force for reciprocatingthe movable rod 81 in the longitudinal direction of the valve body 31 isnot applied.

A structure in which the plate springs 51 attached to the opposite endportions 36 of the valve body 31 differ in elastic force from each othermay be employed.

A structure in which each plate spring 51 is fixed to the main body 41such that its main faces having the largest area extend obliquely (notperpendicularly) to the longitudinal direction of the valve body 31 maybe employed.

A motor, a piezo element, a thermal actuator, or the like may beemployed as the actuator 70. However, the actuator 70 desirably has astructure which generates no frictional force when it drives the valvebody 31. Notably, even in the case where frictional force is generatedin the actuator 70 upon drive of the valve body 31, the responsivenessof the flow path switching valve 10 in switching the flow path can beimproved, as compared with the conventional flow path switching valve,by reciprocating the valve body 31 in a state in which the valve body 31and the main body 41 do not rub against each other.

The number of the ports formed in the main body 41 is not limited tothree and may be two or four or more.

The fluid whose flow passage is switched by the flow path switchingvalve 10 is not limited to air, and may be liquid or gas other than air.

Third Embodiment

In the present embodiment, the above-described movable rod 81 isomitted, and the valve body 31 and the movable element 76 areintegrated. In the below, a portion of the third embodiment differentfrom that of the second embodiment will be mainly described. Notably,members which correspond to those of the first and second embodimentsare denoted by the same reference numerals, and their descriptions willnot be repeated.

As shown in FIGS. 20 to 22, the valve mechanism 20 includes a housing21, the valve body 31, third main bodies 41C, fourth main bodies 41D,plate springs 51, a cover 27, etc. The housing 21, the valve body 31,the third main bodies 41C, the fourth main bodies 41D, the plate springs51, and the cover 27 are formed of a non-magnetic material.

The housing 21 has a rectangular tubular shape. The housing 21 has P0ports (pressurized air ports) to which pressurized air (corresponding tothe fluid) is supplied, an A0 port (output port) from which air issupplied to a load and to which air is discharged from the load, and R0ports (discharge port) from which air is discharged. The P0 ports, theA0 port, and the R0 ports are formed of a non-magnetic material.Pressurization flow passages, an output flow passage, and air dischargeflow passages are connected to the P0 ports, the A0 port, and the R0ports, respectively. The pressurization flow passages and the airdischarge flow passages are connected to the third main bodies 41C. Theoutput flow passage has an opening on the inner wall surface of thehousing 21.

The valve body 31, the main bodies 41C and 41D, the plate springs 51,the magnets 74A, 74B, 75A, and 75B, etc. are disposed inside the housing21. Each of the main bodies 41C and 41D has the shape of a rectangularparallelepiped (the shape of a flat plate). The third main bodies 41Care fixed to the housing 21. The fourth main bodies 41D are fixed to thethird main bodies 41C. The valve body 31 has the shape of a rectangularparallelepiped (the shape of a flat plate).

The valve body 31 is disposed between the fourth main bodies 41Ddisposed in parallel. A gap is formed between each of the fourth mainbodies 41D and the valve body 31. Namely, the valve body 31 does notcontact with the fourth main bodies 41D.

The valve body 31 is fixed to the fourth main bodies 41D through theplate springs 51. Two short-side portions 51 b of each plate spring 51are fixed to the corresponding fourth main bodies 41D. Each plate spring51 is fixed to the corresponding fourth main bodies 41D such that itsmain faces (vertical surfaces in FIGS. 20 and 21) having the largestarea extend perpendicularly to the longitudinal direction of the valvebody 31. By virtue of such a configuration, the valve body 31(corresponding to the movable member) is supported by the pair of platesprings 51 to be movable in the longitudinal direction of the valve body31 (corresponding to the predetermined direction).

Predetermined surfaces 31 a of the valve body 31 are flush withcorresponding first surfaces 41 d of the fourth main bodies 41D. Asshown in FIG. 22, facing surfaces 41 a of the third main bodies 41C facethe predetermined surfaces 31 a of the valve body 31. The first surfaces41 d of the fourth main bodies 41D face the facing surfaces 41 a of thethird main bodies 41C. The third main bodies 41C and the fourth mainbodies 41D are fixed together in a state in which two shims (spacers) 46having a predetermined thickness and arranged side by side are insertedbetween each of the first surfaces 41 d of the fourth main bodies 41Dand corresponding one of the facing surfaces 41 a of the third mainbodies 41C. The thickness of the shims 46 is about 10 μm. Namely, gaps(predetermined gaps) corresponding to the thickness of the shims 46 areformed between the predetermined surfaces 31 a of the valve body 31 andthe facing surfaces 41 a of the third main bodies 41C. Therefore, thevalve body 31 has no portion which is in sliding engagement with othermembers. Notably, the number of the shims 46 is not limited to two, andmay be one or three or more.

As shown in FIG. 22, the valve body 31 has two open flow passages 32which are open to the predetermined surfaces 31 a over a predeterminedlength L1 as measured in the longitudinal direction of the valve body 31(the predetermined direction). The open flow passages 32 penetrate thevalve body 31 in a direction orthogonal to the predetermined surfaces 31a and each have the shape of an oval hole whose length along the majoraxis is the predetermined length L1. Notably, there can be employed aconfiguration in which the open flow passages 32 are recesses formed onthe predetermined surfaces 31 a of the valve body 31 and do notpenetrate the valve body 31.

Each of the third main bodies 41C has a P1b port, an A1b port, and anR1b port (corresponding to the plurality of ports) which are open to thefacing surface 41 a. The P1b port, the A1b port, and the R1b port areformed at intervals L2 in the longitudinal direction of the valve body31. The intervals L2 are shorter than the predetermined length L1. Eachof the third main bodies 41C has connection flow passages 42, 43, and 44which are connected to the P1b port, the A1b port, and the R1b port,respectively. The connection flow passages 42, 43, and 44 are connectedto the above-described pressurization flow passage, output flow passage,and air discharge flow passage, respectively. Notably, the connectionflow passage 43 is connected to the output flow passage through a spaceinside the housing 21. The space inside the housing 21 is sealed by sealmembers 47.

The plate springs 51 apply an elastic force to the valve body 31 inaccordance with the amount of movement of the valve body 31 in thelongitudinal direction of the valve body 31 (a direction orthogonal tothe main faces of the plate springs 51). Specifically, the plate springs51 apply to the valve body 31 an elastic force which is proportional tothe amount of movement of the valve body 31 in the longitudinaldirection of the valve body 31; i.e., the amounts of deformation of theplate springs 51.

Next, the structure of the actuator 70 will be described with referenceto FIGS. 20 and 21. The actuator 70 includes a core 71 (71 c, 71 d), acoil 72, the magnets 74A, 74B, 75A, and 75B, etc.

The core 71 is formed of a paramagnetic material and has a “U” likeshape. The coil 72 is wound around a portion 71 c of the core 71, whichportion corresponds the bottom of the letter U. A pair of straightportions 71 d of the core 71, which portions correspond to the pair ofstraight portions of the letter U, are parallel to each other.

The magnets 74A and 75A and the magnets 74B and 75B are attached to thepair of straight portions 71 d. The magnets 74A and 75A are permanentmagnets formed of a ferromagnetic material. Each of the magnets 74A to75B has the shape of a rectangular parallelepiped. The magnets 74A and75B are attached to the straight portions 71 d of the core 71 such thattheir S poles are located on the side toward the straight portions 71 dof the core 71 and their N poles are located on the side toward thevalve body 31 (the movable element 76). The magnets 74B and 75A areattached to the straight portions 71 d of the core 71 such that their Npoles are located on the side toward the straight portions 71 d of thecore 71 and their S poles are located on the side toward the valve body31 (the movable element 76). The N pole of the magnet 74A and the S poleof the magnet 74B face each other, and the S pole of the magnet 75A andthe N pole of the magnet 75B face each other. The surfaces of themagnets 74A and 74B which face each other are parallel to each other,and the surfaces of the magnets 75A and 75B which face each other areparallel to each other. The magnets 74A and 75A are disposed at apredetermined interval in the longitudinal direction of the valve body31 (hereinafter referred to as the “predetermined direction”), and themagnets 74B and 75B are disposed at the predetermined interval in thepredetermined direction.

The movable element 76 is disposed between the magnets 74A and 75A andthe magnets 74B and 75B with portions of the housing 21 interveningtherebetween. The portions of the housing 21 intervening between themagnet 74A and 74B and the portions of the housing 21 interveningbetween the magnets 75A and 75B are formed to be thin so that magneticfluxes easily pass through these portions. The movable element 76 isformed of a paramagnetic material and has a rectangular tubular shape.The width L3 of the movable element 76 as measured in the predetermineddirection is smaller than the spacing L4 between the end surface of themagnet 74B (74A) on the connection member 24 side and the end surface ofthe magnet 75B (75A) on the cover 27 side. The valve body 31 extendsthrough a hollow space of the movable element 76. The movable element 76is fixed to the center of the valve body 31 in the predetermineddirection. Namely, the movable element 76 is fixed to a portion of thevalve body 31, which portion is located between the pair of platesprings 51. The movable element 76 does not contact with members otherthan the valve body 31.

In the predetermined direction, the movable element 76 is located at thecenter position (neutral position) between the magnet 74A (74B) and themagnet 75A (75B) due to magnetic forces of the magnets 74A, 74B, 75A,and 75B. In this state, the movable element 76 is fixed to the valvebody 31 supported by the pair of plate springs 51 in the natural state.Namely, in the actuator 70, the position of the movable element 76 in astate in which the plate springs 51 support the valve body 31 in thenatural state is set to the neutral position at which theelectromagnetic force for reciprocating the valve body 31 (the movableelement 76) in the predetermined direction is not applied. The actuator70 drives the valve body 31 in the predetermined direction in anon-contact state by means of the electromagnetic force applied to themovable element 76 in a region between the pair of plate springs 51 inthe predetermined direction.

Next, the principle of reciprocating the valve body 31 in thelongitudinal direction of the valve body 31 (the predetermineddirection) by the actuator 70 will be described with reference to FIGS.23 to 25.

In an unexcited state in which no current is supplied to the coil 72 ofthe actuator 70, as shown in FIG. 23, a magnetic field extending fromthe N pole of the magnet 74A toward the S pole of the magnet 74B and amagnetic field extending from the N pole of the magnet 75B toward the Spole of the magnet 75A are generated. In this state, the movable element76 is at rest in the neutral position in the predetermined directionbecause the generated magnetic fields are in balance. In this state,since the pair of plate springs 51 are in the natural state, no force isapplied from the pair of plate springs 51 to the valve body 31. Also, inthis state, the P1b port and the R1b port of each third main body 41Care closed by the valve body 31 as shown in FIG. 22.

In a positive direction excited state in which a current of a positivedirection is supplied to the coil 72 of the actuator 70, a coil magneticfield extending from the upper straight portion 71 d of the core 71toward the lower straight portion 71 d of the core 71 is generated asindicated by an arrow H3 in FIG. 24. Therefore, the magnetic fieldextending from the N pole of the magnet 74A toward the S pole of themagnet 74B and the coil magnetic field strengthen each other, and themagnetic field extending from the N pole of the magnet 75B toward the Spole of the magnet 75A and the coil magnetic field weaken each other. Asa result, the movable element 76 receives a magnetic attraction forcetoward the connection member 24. Thus, as indicated by an arrow F4, thevalve body 31 moves, together with the movable element 76, in thedirection of the arrow F4. At that time, by means of electromagneticforce, the actuator 70 drives the valve body 31 in a non-contact state,whereby the valve body 31 is driven without coming into contact with themain bodies 41C and 41D. When the valve body 31 is driven, the pair ofplate springs 51 apply to the valve body 31 a reaction force which isproportional to the amount of movement of the valve body 31. In FIG. 22,when the valve body 31 is moved toward the connection member 24, the A1bport and the P1b port of each third main body 41C are connected throughthe open flow passage 32 of the valve body 31. Namely, the flow passageof the flow path switching valve 10 is switched.

The same pressurized air is supplied to the P1b ports of the respectivethird main bodies 41C. As a result, the pressure produced by the airflowing toward the valve body 31 from the P1b of one third main body 41Cand the pressure produced by the air flowing toward the valve body 31from the P1b port of the other third main body 41C are canceled out.

In a negative direction excited state in which a current of a negativedirection is supplied to the coil 72 of the actuator 70, a coil magneticfield extending from the lower straight portion 71 d of the core 71toward the upper straight portion 71 d of the core 71 is generated asindicated by an arrow H4 in FIG. 25. Therefore, the magnetic fieldextending from the N pole of the magnet 74A toward the S pole of themagnet 74B and the coil magnetic field weaken each other, and themagnetic field extending from the N pole of the magnet 75B toward the Spole of the magnet 75A and the coil magnetic field strengthen eachother. As a result, the movable element 76 receives a magneticattraction force toward the cover 27. Thus, as indicated by an arrow F5,the valve body 31 moves, together with the movable element 76, in thedirection of the arrow F5. At that time, by means of electromagneticforce, the actuator 70 drives the valve body 31 in a non-contact state,whereby the valve body 31 is driven without coming into contact with themain bodies 41C and 41D. When the valve body 31 is driven, the pair ofplate springs 51 apply to the valve body 31 a reaction force which isproportional to the amount of movement of the valve body 31. In FIG. 22,when the valve body 31 is moved toward the cover 27, the A1b port andthe R1b port of each third main body 41C are connected through the openflow passage 32 of the valve body 31. Namely, the flow passage of theflow path switching valve 10 is switched.

The present embodiment having been described in detail above has thefollowing advantages.

The pair of plate springs 51 apply elastic force to the valve body 31 inthe predetermined direction in accordance with the amount of deformationof the plate springs 51. Since the valve body 31 is supported by thepair of plate springs 51 to be movable in the predetermined direction,the valve body 31 can be movably supported without involving slidingmovement. The valve body 31 is driven in the predetermined direction ina non-contact state by means of electromagnetic force applied by theactuator 70. As a result, no frictional force is produced during thedrive of the valve body 31, whereby the responsiveness in driving thevalve body 31 can be improved. Further, since the valve body 31 isdriven without involving sliding movement, the valve body 31 is free ofwear, and can be used semi-permanently unlike the case of an ordinaryvalve body involving sliding movement.

The valve body 31 is supported by the pair of plate springs 51, andelectromagnetic force is applied to a region between the pair of platesprings 51 in the predetermined direction. Therefore, it is possible toprevent swaying of the valve body 31 when the valve body 31 is driven.

Electromagnetic force is applied to the movable element 76 fixed to thevalve body 31. Therefore, the movable element 76 to whichelectromagnetic force is applied and the valve body 31 can be formed asseparate members, whereby the degree of freedom in designing the valvebody 31 can be increased.

Fluid can be caused to flow, through the connection flow passages formedin the third main bodies 41C, to or from the ports connected to theconnection flow passages. The valve body 31 has the open flow passages32 which are open to the predetermined surfaces 31 a over thepredetermined length L1 in the predetermined direction. Each of thethird main bodies 41C has a plurality of ports which are formed at theinterval L2 shorter than the predetermined length L1 in thepredetermined direction such that the ports are open to the facingsurfaces 41 a of the third main bodies 41C which face the predeterminedsurfaces 31 a of the valve body 31. Therefore, by driving the valve body31 in the predetermined direction by the actuator 70, the state ofconnection of the plurality of ports through the open flow passages 32of the valve body 31; i.e., the flow passage for the fluid, can beswitched.

The predetermined surfaces 31 a of the valve body 31 are flush with thecorresponding first surfaces 41 d of the fourth main bodies 41D, and thethird main bodies 41C and the fourth main bodies 41D are fixed togetherin a state in which the shims 46 each having a predetermined thicknessare disposed between the facing surfaces 41 a of the third main bodies41C and the first surfaces 41 d of the fourth main bodies 41D.Therefore, gaps corresponding to the thickness of the shims 46 can beeasily formed between the predetermined surfaces 31 a of the valve body31 and the facing surfaces 41 a of the third main bodies 41C.

In the actuator 70, the position of the valve body 31 (the movableelement 76) in a state in which the plate springs 51 support the valvebody 31 in the natural state is set to the neutral position at which theelectromagnetic force for reciprocating the valve body 31 (the movableelement 76) in the predetermined direction is not applied. By virtue ofthis configuration, in a state in which the plate springs 51 support thevalve body 31 in the natural state and no electromagnetic force isapplied to the movable element 76 by the actuator 70, the valve body 31can be maintained at the neutral position in the predetermineddirection. Therefore, by controlling the electromagnetic force appliedto the movable element 76 while using the neutral position as areference, the valve body 31 can be easily reciprocated with excellentreproducibility. Further, the flow rate of the fluid in a state in whichno electromagnetic force is applied to the movable element 76 by theactuator 70 can be stabilized at a constant level.

The third main bodies 41C are provided on the opposite sides of thevalve body 31. Each of the third main bodies 41C has the same ports;i.e., the P1b port, the A1b port, and the R1b port. Therefore, bycausing the same air to flow through the P1b, A1b, and R1b ports of onethird main body 41C and flow through the P1b, A1b, and R1b ports of theother third main body 41C, it is possible to cancel out the pressuregenerated by the air flowing toward the valve body 31 from the P1b andA1b ports of the one third main body 41C and the pressure generated bythe air flowing toward the valve body 31 from the P1b and A1b ports ofthe other third main body 41C. Accordingly, it is possible to preventthe valve body 31 from moving in a direction away from the P1b and A1bports due to the pressure of air flowing toward the valve body 31 fromthe P1b and A1b ports. Also, the required rigidity of the plate spring51 can be decreased, and thinner plate springs 51 can be employed.

Notably, the above-described third embodiment may be modified asfollows.

There can be employed a structure in which the pair of plate springs 51support portions of the valve body 31 other than the opposite ends 36;for example, portions of the valve body 31 slightly offset from theopposite ends toward the center of the valve body 31.

The thickness of the shims 46 is not limited to about 10 μm, and may be5 to 10 μm, 10 to 15 μm, or 15 to 20 μm.

FIG. 26 shows the spacing L5 between the outer ends (ends located on theouter side in the predetermined direction) of the two open flow passages32 and the spacing L6 between the P1b port and the R1b port. Therelation between the spacing L5 and the spacing L6 can be changed asfollows:

L6≥L5.  (1)

In this case, as shown in FIG. 27, the flow path switching valve 10 hasa dead zone near the point where the current supplied to the actuator ofthe valve is 0 mA, and can stabilize the start of flow of the fluid.

L6<L5.  (2)

In this case, as shown in FIG. 28, the flow path switching valve 10provides a constant bleeding flow rate in a zone near the point wherethe current supplied to the actuator of the valve is 0 mA, and canenhance the responsiveness in changing the flow rate of the fluid.

L6<<L5.  (3)

In this case, as shown in FIG. 29, the flow path switching valve 10 canbe used as a mixing valve for mixing a fluid flowing from the port P tothe port A and a fluid flowing from the port R to the port A.

The movable element 76 and the valve body 31 may be formed as a singlemember through use of a paramagnetic material. In this case, the movableelement itself serves as the valve body 31 (the movable member), and theopen flow passages 32 are formed on the movable element.

The present disclosure has been described on the basis of embodiments;however, it is understood that the present disclosure is not limited tothe embodiments and structures. The present disclosure encompassesvarious modified embodiments and modifications within the range ofequivalents. In addition, various combinations and forms and othercombinations and forms including one element only, more elements, orless elements fall within the scope of the present disclosure and thescope of the idea.

What is claimed is:
 1. A flow path switching valve for switching a flowpath for a fluid, the flow path switching valve comprising: a valve bodywhich has an open flow passage which is open to a predetermined surfaceof the valve body over a predetermined length in a predetermineddirection; a main body which has a plurality of ports formed atintervals in the predetermined direction shorter than the predeterminedlength and being open to a facing surface of the main body facing thepredetermined surface and has connection flow passages connected to theplurality of ports, respectively; plate springs which are attached toopposite end portions of the valve body in the predetermined direction,respectively, which support the valve body such that a predetermined gapis formed between the predetermined surface and the facing surface, andwhich apply elastic force to the valve body in accordance with an amountof movement of the valve body in the predetermined direction; and anactuator for reciprocating the valve body in the predetermineddirection.
 2. The flow path switching valve according to claim 1,wherein the open flow passage of the valve body is open, over thepredetermined length in the predetermined direction, to thepredetermined surface and to an opposite surface of the valve bodylocated opposite the predetermined surface; the main body includes afirst main body which has a plurality of ports formed at intervals inthe predetermined direction shorter than the predetermined length andbeing open to a first facing surface of the first main body facing thepredetermined surface and has connection flow passages connected to theplurality of ports, respectively, and a second main body which has aplurality of ports formed at intervals in the predetermined directionshorter than the predetermined length and being open to a second facingsurface of the second main body facing the opposite surface and hasconnection flow passages connected to the plurality of ports,respectively; and the plate springs support the valve body such that afirst predetermined gap is formed between the predetermined surface andthe first facing surface and a second predetermined gap is formedbetween the opposite surface and the second facing surface.
 3. The flowpath switching valve according to claim 1, wherein each plate spring isattached to the main body such that main faces of the plate spring whichhave a largest area extend perpendicularly to the predetermineddirection.
 4. The flow path switching valve according to claim 2,wherein each plate spring is attached to the main body such that mainfaces of the plate spring which have a largest area extendperpendicularly to the predetermined direction.
 5. The flow pathswitching valve according to claim 1, wherein a movable element is fixedto a portion of the valve body, which portion is located between theplate springs; and the actuator reciprocates the valve body in thepredetermined direction in a non-contact state by an electromagneticforce applied to the movable element in a region between the platesprings in the predetermined direction.
 6. The flow path switching valveaccording to claim 2, wherein a movable element is fixed to a portion ofthe valve body, which portion is located between the plate springs; andthe actuator reciprocates the valve body in the predetermined directionin a non-contact state by an electromagnetic force applied to themovable element in a region between the plate springs in thepredetermined direction.
 7. The flow path switching valve according toclaim 3, wherein a movable element is fixed to a portion of the valvebody, which portion is located between the plate springs; and theactuator reciprocates the valve body in the predetermined direction in anon-contact state by an electromagnetic force applied to the movableelement in a region between the plate springs in the predetermineddirection.
 8. The flow path switching valve according to claim 4,wherein a movable element is fixed to a portion of the valve body, whichportion is located between the plate springs; and the actuatorreciprocates the valve body in the predetermined direction in anon-contact state by an electromagnetic force applied to the movableelement in a region between the plate springs in the predetermineddirection.
 9. The flow path switching valve according to claim 5,wherein, in the actuator, a position of the valve body in a state inwhich the plate springs support the valve body in their natural state isset to a neutral position at which the electromagnetic force forreciprocating the valve body in the predetermined direction is notapplied.
 10. The flow path switching valve according to claim 3, whereinthe actuator includes a movable rod which extends through the platesprings and the valve body and is attached to the valve body, and theactuator reciprocates the movable rod in the predetermined direction.11. The flow path switching valve according to claim 4, wherein theactuator includes a movable rod which extends through the plate springsand the valve body and is attached to the valve body, and the actuatorreciprocates the movable rod in the predetermined direction.
 12. Theflow path switching valve according to claim 10, wherein the actuatorreciprocates the movable rod in a non-contact state by electromagneticforce.
 13. The flow path switching valve according to claim 11, whereinthe actuator reciprocates the movable rod in a non-contact state byelectromagnetic force.
 14. The flow path switching valve according toclaim 12, wherein, in the actuator, a position of the movable rod in astate in which the plate springs support the valve body in their naturalstate is set to a neutral position at which the electromagnetic forcefor reciprocating the movable rod in the predetermined direction is notapplied.
 15. The flow path switching valve according to claim 1, whereineach of the predetermined surface and the facing surface is finished tohave a predetermined degree of flatness; and the plate springs supportthe valve body such that the predetermined surface and the facingsurface have a predetermined degree of parallelism therebetween.
 16. Amethod for manufacturing a flow path switching valve for switching aflow path for a fluid, the flow path switching valve comprising: a valvebody which has an open flow passage which is open to a predeterminedsurface of the valve body over a predetermined length in a predetermineddirection; a main body which has a plurality of ports formed atintervals in the predetermined direction shorter than the predeterminedlength and being open to a facing surface of the main body facing thepredetermined surface and has connection flow passages connected to theplurality of ports, respectively; plate springs which are attached toopposite end portions of the valve body in the predetermined direction,respectively, which support the valve body such that a predetermined gapis formed between the predetermined surface and the facing surface, andwhich apply elastic force to the valve body in accordance with an amountof movement of the valve body in the predetermined direction; and anactuator for reciprocating the valve body in the predetermineddirection. the method being characterized by comprising: finishing eachof the predetermined surface and the facing surface to have apredetermined degree of flatness; supporting the valve body by the platesprings such that the predetermined surface and the facing surface havea predetermined degree of parallelism therebetween, and fixing the platesprings to the main body in a state in which a gap jig having athickness set on the basis of a size of the predetermined gap isinserted between the predetermined surface and the facing surface, andthen removing the gap jig.
 17. The method for manufacturing a flow pathswitching valve according to claim 16, wherein the open flow passage ofthe valve body is open, over the predetermined length in thepredetermined direction, to the predetermined surface and to an oppositesurface of the valve body located opposite the predetermined surface;the main body includes a first main body which has a plurality of portsformed at intervals in the predetermined direction shorter than thepredetermined length and being open to a first facing surface of thefirst main body facing the predetermined surface and has connection flowpassages connected to the plurality of ports, respectively, and a secondmain body which has a plurality of ports formed at intervals in thepredetermined direction shorter than the predetermined length and beingopen to a second facing surface of the second main body facing theopposite surface and has connection flow passages connected to theplurality of ports, respectively; and supporting the valve body by theplate springs such that a first predetermined gap is formed between thepredetermined surface and the first facing surface and a secondpredetermined gap is formed between the opposite surface and the secondfacing surface.
 18. The method for manufacturing a flow path switchingvalve according to claim 16, wherein a movable element is fixed to aportion of the valve body, which portion is located between the platesprings; and the actuator reciprocates the valve body in thepredetermined direction in a non-contact state by an electromagneticforce applied to the movable element in a region between the platesprings in the predetermined direction.
 19. The method for manufacturinga flow path switching valve according to claim 17, wherein a movableelement is fixed to a portion of the valve body, which portion islocated between the plate springs; and the actuator reciprocates thevalve body in the predetermined direction in a non-contact state by anelectromagnetic force applied to the movable element in a region betweenthe plate springs in the predetermined direction.
 20. The method formanufacturing a flow path switching valve according to claim 16, whereineach plate spring is attached to the main body such that main faces ofthe plate spring which have a largest area extend perpendicularly to thepredetermined direction; and the actuator includes a movable rod whichextends through the plate springs and the valve body and is attached tothe valve body, and the actuator reciprocates the movable rod in thepredetermined direction.